The manufacture of blow moulded articles for use as vehicle parts is known. In the case of larger vehicle parts which are provided for either structural applications, or which, as a result of design requirements, are required to provide bend or deformation resistance, conventionally one or more rib-like reinforcing webs are moulded directly into the part sidewall.
FIG. 1 shows a cutaway perspective bottom view of a prior art blow moulded running board 10 produced in accordance with conventional manufacturing processes. The running board 10 is formed by blow moulding a thermoplastic resin parison in a mould having a desired overall elongated shape. After moulding, the running board 10 is formed having a generally hollow interior 100 which is delineated by a moulded resin sidewall 12, and which defines generally parallel spaced and longitudinally extending upper tread and bottom surfaces 18,20 which are joined to each other along the respective front and rear sides by forward and rear side webs 22,24.
As shown in FIG. 1, the bottom surface 20 of the running board 10 is adapted for mounting at its end and mid-portions, against three or more L-shaped steel brackets (brackets 28a,28b shown), which in turn are secured directly to a side of a vehicle frame (not shown). To facilitate proper positioning and mounting, the bottom surface 20 may include a series of moulded spaced recesses 30. Each recess 30 is moulded directly into the sidewall 12 and is sized for alignment and juxtaposed engagement with an associated bracket 28, respectively.
The sidewall 12 further defines a series of longitudinally aligned V-shaped reinforcing webs 32 formed in the bottom surface 20, and which extend between the recesses 30. As shown in the cutaway view, the reinforcing webs 32 are formed with an upwardly tapering V-shape and terminate at an uppermost bight immediately adjacent to the underside 18a of the upper tread surface 18. The taper angle of the V-shape of the reinforcing webs 32 is chosen to prevent the running board 10 from binding within the mould following its formation, and facilitate its removal therefrom after moulding operation.
The inventors have appreciated that conventional prior art running boards 10 suffer various disadvantageous. In particular, as a result of their angular geometry, the V-shaped reinforcing webs 32 achieve less structural reinforcement than, for example, a planar I beam or vertical-web reinforcement designs. In addition, as a result of mould limitations, it is not possible to provide reinforcing structures between the running board upper tread surface 18 and the moulded bracket recesses 30. As a result, conventional blow moulded running boards 10 suffer the disadvantage that in their design, unreinforced weakness points exist which could result in premature deformation and/or part failure in the event of loading.